Originally Posted by
Barry2
John,
...
If I turn the pedals manually and very slowly, I can see the chain hang on what appears to the the tooth profile and it does it twice per revolution.
I can mark the teeth with a pen, hold the cassette and rotate the wheel to any point and it's still the same teeth that hang the chain.
By rotating the wheel I prove it's not axle related.
I can use any piece of the chain and the teeth that have the issue remain the same, this proves it's not a bad spot on the chain.
I changed cassette to Dura-Ace and same issue, this proves I didn't get a bad Ultegra cassette.
Still Stumped
Barry
The OP mentioned 5th cog, but not sure if that is also a 21T on their cassette. Perhaps, the die used to cut or stamp the 21T is amiss. I realize this happened on both Ultegra and Dura Ace cogs, but perhaps the same die is used? I'm just speculating it could be a manufacturing process error.
I know the OP said not to mention the other brand S, but for the sake of science trying a SRAM cassette would be a good data point. And since cassettes are wear items, you can keep it for future use.